The hydraulic tools using hydraulic pressure include: a type in which a hydraulic motor is driven by using as an electric power source a battery pack in which batteries are built in, a hydraulic pump is driven by the rotational driving of the hydraulic motor to feed the hydraulic pressure to a hydraulic cylinder and move a piston; and a type in which a piston is moved by receiving feed of hydraulic pressure from a hydraulic-pressure feeder which is separately arranged. In addition, for example, the crimping tools in which a movable die as a movable tool is moved by movement of a piston to connect a crimp contact to an end of an electric wire are known (See Patent. Literature 1).
In order to reduce dead time, increase operational efficiency, and reduce operational time of the movable die as the movable tool, a fast-feed piston for quickly moving the movable die in a free state is built in the above hydraulic tools.
FIG. 5 is a cross-sectional view illustrating the structure of a conventional hydraulic tool, FIG. 6 is a cross-sectional view along the line C-C indicated in FIG. 5, and is a magnified sectional view illustrating a rotation stopper for a conventional fast-feed piston.
As illustrated in FIG. 5, a piston 32 and a fast-feed piston 34 are inserted in a body 31 of the conventional hydraulic tool 30. Hereinafter, the body 31 side is referred to as the front end portion, and an oil tank 9 side is referred to as the rear end portion. In addition, in each part, a fixed tool 13 side is referred to as the front end portion, and the oil tank 9 side is referred to as the rear end portion.
<Body 31>
In the body 31 of the conventional hydraulic tool 30, a large, first cylinder chamber 31a, a female thread 31b, and a female thread 31c are formed in the body 31. A connection portion 34a of the fast-feed piston 34 is screwed into the female thread 31b, and the female thread 31c fixes a setscrew 36 as a rotation stopper for the fast-feed piston 34.
<Piston 32>
A piston 32 is arranged in the first cylinder 31a through a rectangular-wire helical spring 33. In addition, a fast-feed piston 34 is inserted in a second cylinder chamber 32a arranged at the end face of the piston 32.
<Fast-Feed Piston 34>
In the fast-feed piston 34, a trunk portion is formed by enlarging the diameter in a front end portion (on the left side in FIG. 5) and a connection portion is formed by reducing the diameter in a rear end portion, and a male thread is formed in the tip end portion of the connection portion 34a. The male thread is screwed into the female thread 31b in the body 31 so that the fast-feed piston 34 is integrally fixed to the body 31. In addition, a male thread 34d is formed in a rear end portion 34e of the trunk portion of the fast-feed piston 34, and a U-nut 35, in which backlash (gap) is eliminated for preventing loosening, is screwed onto the male thread 34d, so that the U-nut 35 is integrated with the fast-feed piston 34.
Further, as illustrated in FIG. 6, a rotation stopper with the U-nut 35 is constituted by using one of four grooves 35a arranged in the U-nut 35.
As illustrated in FIG. 6, the groove 35a is a groove having a U-shaped cross section defined by the lines, c-e, c-d, and d-f.
The lines c-e and d-f are parallel to the line o-g connecting the center point o of the fast-feed piston 34 and the center point g of the setscrew 36. In addition, the line c-d is perpendicular to the line o-g. Further, the contact points of the setscrew 36 and the groove 35a are the points e and f. Furthermore, the setscrew 36 is not in contact with the line c-d, and is close to the line c-d and separated from the line c-d by a gap t.
In other words, the rotation stopper for the conventional fast-feed piston 34 prevents rotation in the loosening direction (indicated by the arrow→-) as illustrated in FIG. 6, by engagement, with the setscrew 36, of the point f on the groove 35a in the U-nut 35 (which is integrally fixed to the fast-feed piston 34).